You get 1 potato per 60 seconds per game if you lose, and 1 potato per 30 seconds per game if you win. To get your potatoes you have to shoot someone within the last 60 seconds of a round. The time is how much time you played the round, rounded down if necessary.

Don't look at the link because few things are misleading, go here instead it's a lot more accurate.

Weapons like the AN 94 don't inflict 2 or 3 but 2.5, the game don't show such things (including health) it's only full numbers.

Rushing on maps like the submarine map often lead rushers to their death, being the void or an awesome ambush, people like to put a land mine at the edge and a good way to slow down rushers is to fill the map with conjuration to stop them in tiny holes for a moment, one of the best battlefield for the UMP 45 if you make sure you have a path so you can move around the place.